How to Convert SPI Data Correctly?

[koukileo]

I have an ADC of ADS1256, I try to use Myrio to read the data via SPI, but I get stuck when converting the data~ Can you help how to get the correct data?(ADS1256datasheet )

I gave a set of ARDUINO's code which works fine, and I tried to emulate his conversion without success.

I'm trying to put this code on labview now, can anyone help me?

Spoiler

adc_val[i] = SPI.transfer(0);
adc_val[i] <<= 8; //shift to left
adc_val[i] |= SPI.transfer(0);
adc_val[i] <<= 8;
adc_val[i] |= SPI.transfer(0);

for (i=0; i <= 2; i++){ // Single ended Measurements
if(adc_val[i] > 0x7fffff){ //if MSB == 1
adc_val[i] = adc_val[i]-16777216; //do 2's complement
} 

 Where am I doing wrong?

Note, FORLOOP is used to read multiple values ​​consecutively.

[GerdW]

Hi koukileo,

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@koukileo wrote:
adc_val[i] = SPI.transfer(0);
adc_val[i] <<= 8; //shift to left
adc_val[i] |= SPI.transfer(0);
adc_val[i] <<= 8;
adc_val[i] |= SPI.transfer(0);

for (i=0; i <= 2; i++){ // Single ended Measurements
if(adc_val[i] > 0x7fffff){ //if MSB == 1
adc_val[i] = adc_val[i]-16777216; //do 2's complement
} 

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What about this one:

[koukileo · Accepted solution]

Thanks for your reply, I finally understand my problem, the ADC is 24bit data, so I want to divide it into three sections with 8bit. The code is as follows~

Code part from this article: SPI on myRIO with synchronous 8 channel ADC

[koukileo]

Your code is great too~ Made me understand new ways.

[GerdW]

Hi koukileo,

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@koukileo wrote:

Thanks for your reply, I finally understand my problem, the ADC is 24bit data, so I want to divide it into three sections with 8bit. The code is as follows…

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Quite convoluted!

Whenever you start to copy&paste the same code several times you should think about using a loop to call that code repeatedly! (And when you combine this with LabVIEW autoindexing feature it becomes really easy…)

[koukileo]

Thanks for your advice~ I forgot to have this method. Thank you very much~

[GerdW]

Hi koukileo,

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@koukileo wrote:

Thanks for your advice~ I forgot to have this method. Thank you very much~

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Why use a loop (or duplicated code) at all when you only need the result of the first iteration?

[koukileo]

What you can see in the picture is to demonstrate the use.
I actually have a 3-axis accelerometer, so I end up needing 3 DATA~
Best regards